(A) Protein levels of Tyrosinase (TYR), Tyrosinase-related protein 1 (TYRP1) and Silver (SL) were downregulated in NRG1-treated cultures (22 days after treatment). MITF and DCT expression was not visibly altered by NRG1. (B) A time-course analysis of MITF expression at 10, 60, 180, and 360 minutes after addition of NRG1. MITF phosphorylation (upper MITF band) was increased by NRG1 at 180′ and protein levels were decreased by NRG1 after 360 minutes, indicating that activation of ERBB3 pathway can regulate MITF activity levels.